1. Field of the Invention
The present invention relates to a push-on switch that is used as an operating switch for an input operation unit in an electric apparatus including an electric component such as a car air-conditioner, and audiovisual equipment.
2. Background Art
In recent years, a push-on switch has been widely used as an operating switch for an input operation unit in an electric apparatus including a car air-conditioner and audiovisual equipment. A description will be made for such a conventional push-on switch, using FIG. 7.
FIG. 7 is a sectional view of the conventional push-on switch. In FIG. 7, case 1 is a case made of insulating resin, open at its top. Fixed contact 2 (2A and 2B), made of a pair of metal plates, is insert-molded to be fixed to the central part of inner bottom surface 1A of case 1.
The bottom end of movable contact 3, made of an elastic thin metal plate, formed in a dome shape, and open at its bottom, is placed on fixed contact 2B disposed at the outer position. In this case, the bottom surface of movable contact 3 maintains a clearance of the height of the dome from fixed contact 2A at the central position that corresponds to the position below the central top of movable contact 3.
Power driver 4, made of rigid material, is placed movably up and down on the central top of the above-mentioned movable contact 3. This power driver 4 is composed of flange 4A, annularly formed at the position of an intermediate height; lower pressing part 4B, with a small diameter, projectingly formed on the bottom surface of flange 4A; and operating projection 4C, projectingly formed on the top surface of lower pressing part 4B. The bottom surface of the above-mentioned lower pressing part 4B touches the central top of the above-mentioned movable contact 3.
Meanwhile, operating projection 4C of power driver 4 projects upward through a through-hole disposed on cover 5. The cover 5 is combined with case 1 so as to cover the opening of case 1, where the top surface of flange 4A of power driver 4 touches the bottom surface of cover 5 in a non-operational state.
The conventional push-on switch with the structure as mentioned above is mounted to a cabinet or the like so that a pressing operation can be performed with set knob 7, which is an operation button in the electric apparatus, disposed movably up and down, as shown in FIG. 7.
When operating projection 4C of power driver 4 is pressed through the above-mentioned set knob 7, the central top of movable contact 3 is immediately pressed by lower pressing part 4B provided on the bottom of power driver 4, and then a given force causes movable contact 3 to invert at its central part with comfortableness (i.e., with a comfortable feeling to the operator). Consequently, the bottom surface of movable contact 3 touches centrally-disposed fixed contact 2A; and then externally-located fixed contact 2B short-circuits with centrally-located fixed contact 2A through movable contact 3, to enter a switch-on state.
Movable contact 3, when pressing of power driver 4 is stopped, returns to its original, upwardly convex dome shape, with comfortableness, owing to its own restorative force, to separate from centrally-positioned fixed contact 2A. Then, power driver 4 is pressed back upward according to the restorative action, to enter the original switch-off state shown in FIG. 7.
Here, information on prior art documents related to the present invention includes Japanese Patent Unexamined Publication No. 2002-343178.
However, in the above-mentioned conventional push-on switch, small dimensional tolerance is required for the parts of the electric apparatus in order to incorporate set knob 7 for pressing down power driver 4, without rattle.